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Appendix TL

789

clay ironstone being (according to Bloxam) for every ton of iron

smelted—                , ~ . .     , ^                                  0

i Calcined Ore......        4$ c\vt

Grey Cast Iron   < Coal         ..........        50

( Limestone           ...        ...        17

( Calcined Ore
\ Hematite...
\Vhite. Cast Iron X Forge Slag

Coal
( Limestone

28
10

10

42
14

and one-third more air is supplied in the second case. Hematite
is a very pure red ore containing some 70% of iron, while the
above-mentioned ore will never have more than 50%,

JP. 74. Cast Iron (Effect of Elements).

Carbon exercises the greatest change in cast iron, and its
effects have been well explained.

Silicon, after carbon, is the most useful element. If present
up to 3!% it produces soft, strong, grey iron ; and if added to a
hard, whitish, and cheap iron, it will make it strong and grey. It
is now much used to improve poor irons, but should only be
present in small quantities in iron that is to be chilled.

Sulphur is prejudicial, causing blowholes : it should not
exceed '15 %.

Phosphorus is also harmful, for though giving fluidity, it pro-
duces brittlen ess if in excess of i%.

Manganese tends to dissolve the graphite and promote com-
bined carbon, and confers the property of chilling. If more than
i% it causes large crystals as in Spiegeleisen. Rapid solidifica-
tion also favours combined carbon (see Chilling, p. 34);

The following foundry irons are the mean of many good
specimens :

WOOLWICH, 1858,

*
	Graphite.
	Si.
	P.
	S.
	Mn.

Percentages
	2*59
	i '42
	'39
	•06
	*5*   .